Many civil and aerospace engineering structures are designed for ease of transport and storage, weight and financial economy. For these reasons, a number of inflatable and rigidizable structures have been developed. One problem which has not been fully addressed is the issue of providing uniform rigidization throughout the structure, particularly when larger structures or assembled structures are constructed. Some relevant examples of prior art include the following.
U.S. Pat. No. 3,098,229, issued to Raabe, discloses an inflatable and rigidizable transmission line. The transmission lines are prefabricated and folded or rolled up into a package. At a desired time, the transmission line is unfurled and inflated to a deployed position by injecting an expansible material into the interior of the transmission line. One embodiment consists of two concentric plastic tubes. The innermost tube is inflated to deploy the structure. Rigidizable material is subsequently injected into the space between the inner and outer tubes. However, Raabe does not provide a gas escape mechanism to relieve out gassing of the rigidizable material. Nor does Raabe address the issue of uniform injection of rigidizable material.
U.S. Pat. No. 3,110,552, issued to Voelker describes a structure having an inner cavity surrounded by double walls. The inner cavity can be inflated to give the structure a desired shape. A metered amount of mixed chemicals, which foam and rigidize upon heating is deposited between the double walls. The rigid foam provides structural support. The invention also includes a vent to permit escape of excess gases released from the foam. However, the invention does not suggest a specific venting or escape mechanism design configuration nor address specific issues such as gas escape optimization and pressure barrier build up. Nor does Voelker address the issue of distributing foam uniformly throughout the double walls.
U.S. Pat. No. 5,058,330, issued to Chow discloses a spheroidal habitat structure having a pressurizable inner core and fabric layer walls. Rigidizable foam is filled in between the fabric layers to provide structural strength. The invention does not address rigidization of extended structures.
U.S. Pat. No. 3,405,886, issued to Gosnell discloses a method of making an inflatable erectable hollow structure. The structure walls are fabricated from a plastic impregnated wall material. The walls are then treated with a non-permanent softening agent, and collapsed into a container. The structure can be inflated and venting orifices are provided for venting exhaust gases emanating from the softening agent.
U.S. Pat. No. 5,044,579, issued to Bernasconi discloses curable inflatable flexible tubes that form the skeleton of a larger structure. The tubes are prefabricated, pre-assembled, and coated on the inside with a curable laminate. The assembly can be inflated and unfolded using a single pressure source. Rigidization is achieved using a gaseous chemical catalyser injected in the same way as the pressurizing gas. The unfolding rate is controlled using a series of valves and diaphragms in the connectors between the tubes.
U.S. Pat. No. 4,880,186 issued to Mecca discloses a prefabricated structure deployed from a container using pressurized foam. The structure is a cylindrical double walled structure formed from a flexible material. The walls are initially bonded together with adhesive when the structure is folded inside a container. Foam injected between the walls at an annular edge releases the walls and deploys the structure.
U.S. Pat. No. 5,339,574 issued to Downing discloses an inflatable rigidizable structure consisting of at least three flexible walls. The flexible walls define an innermost cavity and an outermost cavity. The outermost cavity is pressurized with gas to give the structure shape. The innermost cavity is then injected with curable mold material to rigidize the structure. The outermost cavity can then be deflated and injected with curable mold.
It is an objective of the present invention to provide an inflatable structure that is capable of being remotely and inflatably deployed. It is a further objective of the invention to provide a container to package and controllably deploy the structure. It is a further objective that such a structure can be rigidized by injecting a rigidizable fluid into the walls of the structure. It is a further objective that the rigidizable fluid be injected and distributed uniformly throughout the walls to prevent deformations or weaknesses in the structure. It is a further objective that the invention can be scaled to relatively large sizes, or assembled with other similar structures using the same technology. It is still a further objective that the structure may be used to deploy and erect other structures. Finally, it is an objective to provide a structure that is simple and inexpensive to produce while fulfilling all of the described performance criteria. While some of the objectives of the present invention are disclosed in the prior art, none of the inventions found include all of the requirements identified.